We will continue to explore temperature regulation in hibernating rodents exposed to freezing cold while monitoring oxygen consumption, heart and respiratory rate and body temperature. We will continue our studies on the non-shivering thermogenesis which we observe in hibernating rodents when they are regulating their body temperature, including the role of the sympathetic nervous system in mobilizing brown fat. We will also continue our attempts to make discrete lesions in the preoptic-anterior hypothalamic area and will record the response of lesioned, hibernating animals when exposed to lethal cold.